Published German patent application DE-A 3,248,679 discloses a lawn mower having a fixed blade and a rotating knife. The cutting apparatus includes a drive motor which imparts rotational movement to the knife whereby the knife and blade slide toward each other in a relative movement. The fixed blade has several cutting edges as has the rotating knife with these cutting edges being brought into cutting engagement so that they cut the grass blades in a manner similar to scissors. In the known arrangement, the cutting surfaces of the blade are configured so as to be curved and extend approximately in the tangential direction to an approximately circular-shaped center part of the blade. Two sections of the circular periphery are provided with long cutting surfaces and two sections of the peripheral surface are provided with short cutting surfaces. The rotating knife has extended cutting surfaces which likewise are arranged tangentially to the circular-shaped center portion of the knife.
In the known arrangement, the blade and knife have a complicated form and the number of cutting surfaces is limited because of the tangential direction of these cutting surfaces. The number of cutting surfaces is especially limited when it is intended that a high cutting capacity be achieved with the long cutting edges. The configurations of the cutting surfaces on the blade are different over the periphery and are unsuitable for cutting work with the so-called scythe movement. These configurations furthermore lead to a heavy embodiment of knife and blade whereby the cutterhead is very heavy and therefore requires a corresponding expenditure of effort by the operator.
U.S. Pat. No. 4,483,070 discloses measures which facilitate the manipulation of such apparatus for the operator with respect to its weight. However, such measures limit the freedom of movement of apparatus of this kind and require a bendable drive shaft between the drive motor and the rotating knife with the drive motor being strapped to the back of the operator.